This proposal will investigate the relationship of immunoregulation to histopathology and disease activity in human and murine Non-Hodgkins lymphomas (NHL) and explore the potential of monitoring treatment in NHL using flow cytometric analyses of peripheral blood mononuclear cells (PBMC). One aspect of this application will involve an examination of the various mononuclear subpopulations in both involved tissue and peripheral blood at diagnosis. This will include cell surface marker analysis of monoclonal B-cell populations; total T-cells as well as functional T-cell subsets and monocytes. In addition in vitro functional analyses of both tissue and blood will be performed. This will include mitogenic and antigenic reactivity and antigen specific T and non-specific T and monocyte suppressor cell activity. A second aspect of this proposal (human and murine) will evaluate the effects of treatment on both the malignant and residual normal mononuclear cell subpopulations. This will include cell surface marker analysis as above and a sequential comparison of population histograms generated by flow cytometric analysis. These studies will be performed at diagnosis (tissue and PBMC); when treatment begins (PBMC) and every two months thereafter for the duration of the proposal. The histograms generated will be compared to those obtained at diagnosis to determine if flow cytometric analysis of PBMC is predictive of therapeutic outcome in NHL. The final aspect of this proposal will evaluate the relationship of immunoregulation to histopathology and disease activity. This will involve separation of immunoregulatory cell types by fluorescence activated cell sorting in humans to alter PBMC reactivity in vitro and in mice to assess their effects in vivo and in vitro. These studies have the potential to better delineate the immunologic aberrations in NHL; the relationship of immunoregulation to histopathology and disease activity; and the utility of flow cytometric analysis of PBMC to predict therapeutic outcome. As such, they should increase our understanding of the basic immunobiology of NHL and serve as a basis for designing future therapeutic studies.